Small fire remains a day after major Philadelphia refinery blast

A small fire was burning at the Philadelphia Energy Solutions plant on Saturday, a day after a massive blaze ripped through the largest oil refinery on the U.S. East Coast, city officials said.

Several explosions sent a huge fireball into the sky in the early morning hours of Friday, engulfing the surrounding areas in smoke after a fire started in a tank at the 335,000 barrel-per-day refining complex, also the oldest in the Northeast.

Four workers were injured, according to a company statement, and treated on-site, while city emergency workers treated one person, who did not need to go to a hospital.

The plant was likely to remain shut for an extended period, according to Philadelphia city officials and company sources.

"A very small fire remains on the unit impacted," the city of Philadelphia said in a statement, citing the company as its source.

"PES continues to work to isolate the remaining line and PFD (Philadelphia Fire Department) emergency responders remain on scene to monitor the area."

The fire department's hazardous materials task force was monitoring air quality every two to three hours, the city said, focusing on the perimeter of the refinery and surrounding neighborhoods.

"As has been the case since Friday morning, the city has no findings that would point to any immediate danger in the surrounding community at this time," the statement said.

PES said on Friday it believed the product that was burning was "mostly propane."

An estimated 300,000 people live within three miles (5 km) of the Philadelphia refinery.

(Reporting by Daniel Trotta, editing by G Crosse)